xe2x80x9cResinxe2x80x9d is a generic term used to describe both natural and synthetic glues which derive their adhesive properties from their inherent ability to polymerize in a consistent and predictable fashion. The vast majority of modern industrial resins are synthetic, and are normally derived from petroleum feedstocks. Two of the most important classes of synthetic resins, in terms of production volume and total sales are phenol formaldehyde (P/F) and urea formaldehyde (U/F) resins. In both cases, the principal market application is for use as a glue binder in man-made wood products.
Phenol formaldehyde (P/F) resin, because of its resistance to moisture, has a particular value in external (outdoor) or damp environments. It is therefore, the leading adhesive used for the manufacture of plywood, oriented strand board (OSB) and wafer board (Sellers, 1996). P/F resins are also widely used in laminates, insulation, foundry materials, moulding compounds, abrasives and friction materials for the transportation industry (i.e., clutch facings, disk facings and transmission components). As its name suggests, the principal ingredients in P/F adhesives are phenol and formaldehyde. However, the finished product is actually a mixture of P/F, caustic, and water. Assorted fillers, extenders and dispersion agents may then be added for specific adhesive applications.
The formaldehyde ingredient in P/F resin is derived from methanol, normally produced from natural gas. The phenol ingredient is typically manufactured from benzene and propylene via a cumene intermediate. In addition to P/F adhesive manufacture, phenol is used in the manufacture of other important products, for example, Bisphenol A and Caprolactam. Bisphenol A is a principal component in polycarbonates used in automotive parts, compact discs and computer discs, and Caprolactam is a raw material for Nylon 6, used within stain resistant carpets.
When mixed together in water and with caustic added as a catalyst, phenol and formaldehyde undergo a condensation reaction to form either ortho- or para-methylolphenol. The resultant PF resin, as shipped to market, is a dark brown liquid which is polymerized and cross-linked to an intermediate degree. It is then cured in the final board, laminate or other product without catalyst simply with the addition of heat at which time the final polymerization and cross-linking take place via condensation reactions. The release of free formaldehyde during the resin manufacture and resin use stages is a concern from a health and safety perspective. Furthermore, the costs associated with formaldehyde production have increased and there is a need in the art for alternative materials for use as wood adhesives and binders.
One alternative for phenol that has been considered are lignins which have been recovered from wood, wood residues, bark, bagasse and other biomass via industrial or experimental processes. Natural lignin (i.e. the polymer which occurs in nature which holds wood and bark fibres together and gives wood its strength) and P/F formaldehyde resins are structurally very similar. Lignin is a random network polymer with a variety of linkages, based on phenyl propane units. Lignin-based adhesive formulations have been tested for use within plywood, particle board and fibre board manufacture. The addition of polymeric lignin to P/F formulations has been found to prematurely gel the P/F resin thereby reducing shelf life, limiting permeation of the lignin-P/F resin into the wood and producing an inferior mechanical bond (Kelley 1997). It is important to note that lignins which are isolated and recovered from biomass, and which have been tested in resin formulations, are not identical to the natural lignin present in the original biomass, but are altered somewhat by the recovery process. Some examples of recovered lignins which have been tested in PF resin formulations are Kraft lignin, lignosulphonates, Alcell(trademark), Organocell(trademark), pyrolytic lignin and natural resin of the present invention.
Pyrolysis of lignin has been considered as a potential approach to upgrading lignin to more usable phenolic type resins. While relatively mild thermal or thermo-catalytic processing at low pressures can be used to break the lignin macromolecules into smaller macromolecules, lignin segments and monomeric chemicals, such procedures may cause condensation reactions producing highly condensed structures such as char and tar, rather than depolymerized lignin fragments or monomeric chemicals.
A further alternative for the production of phenolic compounds involves use of pyrolytic pitch oils produced in the rapid destructive distillation (fast pyrolysis) of wood and other biomass. These pyrolytic oils are comprised of a complex mixture of compounds including phenolic compounds, guaiacol, syringol and para substituted derivatives, carbohydrate fragments, polyols, organic acids, formaldehyde, acetaldehyde, furfuraldehyde and other oligomeric products (Pakdel et al 1996). However, wood-derived lignin and lignin-rich pyrolytic bio-oils have lacked consistency and have exhibited inferior properties when compared with phenol-formaldehyde resins (Chum et al. 1989; Scott 1988; Himmelblau 1997; Kelley et al., 1997).
Due to the complexity of pyrolytically-derived bio-oils, further processing is required in order to obtain suitable fractions useable as a replacement for phenol, or to be considered as an extender for petroleum-derived phenol within P/F resin formulations. Typically the phenolic derived from pyrolysis oils requires separation prior to use in order to remove impurities. One such method involves water extraction of the whole-oil, followed by precipitation and centrifugation or filtration and drying of the non-aqueous fraction to prepare a xe2x80x9cpyrolytic ligninxe2x80x9d fraction (Scott 1988). However, adhesive formulations prepared using pyrolytic lignin were found to be inferior to P/F resin formulations in both colour and odour, and required long press times in order to avoid de-lamination of waferboards. Tests indicated that none of the pyrolytic lignin samples meet the internal bond (IB) test requirement (Scott 1988, see pp. 91-92).
In U.S. Pat. No. 4,209,647 (Jun. 24, 1980) a fractionation method for the preparation of a phenol-enriched pyrolytic oil is disclosed which involved a multistep process that selectively solubilized neutral phenols, and organic acids of the whole-oil with NaOH followed by extraction with methylene chloride. However, this multistep process is costly, laborious, time consuming and involves the use of volatile solvents that are known to be health threatening.
Another fractionation method involves adding ethyl acetate to whole-oil pitch to produce ethyl acetate soluble and insoluble fractions. The ethyl soluble fraction is then isolated and the ethyl acetate evaporated to isolate a fraction containing phenolic and neutrals (P/N) derived from the pyrolytic oil (Chum et al. 1989, U.S. Pat. No. 4,942,269, Jul. 17, 1990, and U.S. Pat. No. 5,235,021, Aug. 10, 1993). Preliminary results with the P/N fractions revealed that fractionated pyrolytic oils could be used within P/F resin compositions, as P/N containing resins exhibited equivalent gel times as noted for P/F resins. However, the fractionation protocol is not suitable for industrial scale production, nor is this process cost effective for the preparation of alternative components for use within P/F resins at a commercial scale (Kelley et al., 1997).
All of the process disclosed within the prior art as outlined above involve the extraction of a phenol-enhanced fraction from the whole pyrolytic oil product using complex protocols involving precipitation, followed by centrifugation or filtration, or the use of solvents and alkali. None of the prior art discloses methods for the production of a bio-oil which is readily prepared from the whole pyrolytic oil or that exhibits properties suitable for adhesive use. Furthermore, the prior art does not disclose methods directed at producing a fraction of bio-oil suitable for adhesive use, yet that is simple to produce and that does not require any solvent extraction.
It is an object of the invention to overcome disadvantages of the prior art.
The above object is met by the combinations of features of the main claims, the sub-claims disclose further advantageous embodiments of the invention.
The present invention relates to the production and use of a natural resin, a highly reactive ligninic product, derived from wood, bark and other biomass residues using rapid destructive distillation, for example, fast pyrolysis. Specifically, the natural resins (NR) of this invention are obtained from the fast pyrolysis of wood products. The NR is obtained from a ligninic fraction of the liquid pitch product produced from fast pyrolysis of biomass.
By the processes of the present invention, there is no need to extract a phenol enhanced portion using solvents, water induced solids separation, or alkali. Rather the NR of this invention may be produced from a selected product fraction of the whole-oil obtained from the pyrolytic process, or from the whole-oil product. The whole-oil, selected product fraction, or a combination thereof, is processed in a manner that reduces non-resin components including odorous components and acids in order to produce NR. Such a processing step involves distillation/evaporation.
The natural resins (NR) of the present invention can be used as a substitute for some of the phenol in phenol/formaldehyde, phenol urea formaldehyde, and phenol melamine urea formaldehyde resins used as adhesives in the manufacture of wood products, or the NR can be used as a substitute of some of the phenol and some the formaldehyde components of phenol-containing formaldehyde resins, for example industrial phenol-formaldehyde resins. Furthermore, the NR of this invention can be used as a substitute within urea formaldehyde resins, and melamine urea formaldehyde, and related resins. The natural resins of the present invention can be used as a substitute for either some of the phenol component of a phenol-containing formaldehyde resin or for both the phenol and formaldehyde components of the resin, or as a substitute within urea formaldehyde type resins.
The natural resins of the present invention exhibit high reactivity due to the presence of a high number of active sites for binding and cross linking during polymerization.
According to the present invention there is provided a method of preparing a natural resin (NR) comprising:
i) thermally converting a suitable biomass via rapid destructive distillation in order to produce vapours and char;
ii) removing the char from the vapours;
iii) recovering the vapours to produce a liquid pitch product;
iv) processing the liquid product using distillation/evaporation to produce the NR.
The present invention embraces the above method, wherein the step of processing uses the liquid product obtained from a primary recovery unit, a secondary recovery unit, or a combination thereof.
This invention also pertains to the above method wherein the step of processing comprises the addition of water to the NR to produce an NR with reduced viscosity.
This invention relates to the above method wherein the step of processing comprises removing essentially all of the water content of the NR to produce a solid NR.
Furthermore, the present invention relates to the method as defined above wherein the step of processing comprises pretreating the liquid product prior to distillation/evaporation. Preferably, the step of pretreating comprises a water wash to reduce viscosity, improve flowability into downstream equipment and enhance the removal of non-resin components.
This invention is also directed to a natural resin (NR) characterized by comprising a water content up to about 20%, pH of about 2.0 to about 5.0, and acids content from about 0.1 to about 5 (dry wt %) and a viscosity of about 6 to about 130 cST (@70xc2x0 C.) for liquid NR, or the NR may be solid NR.
This invention is also directed to a resin composition that comprises the NR as defined above. Furthermore, this invention is directed to a resin composition comprising NR from about 1% to about 40% (w/w) of the resin composition.
This invention is also directed to a resin composition as defined above comprising a phenol-containing or urea containing formaldehyde resin. Furthermore, this invention relates to a resin composition as defined above wherein the phenol-containing or urea-containing formaldehyde resin is selected from the group consisting of phenol formaldehyde, urea formaldehyde, phenol melamine urea formaldehyde, melamine urea formaldehyde, and phenol urea formaldehyde.
This invention also relates to a resin composition as defined above wherein the NR comprises from about 20 to about 40% (w/w) of the resin composition. Furthermore, the resin composition of this invention may further be characterized in that a portion of the formaldehyde, within the formaldehyde-phenol resin is replaced with NR, and wherein the NR replaces up to about 50% of the formaldehyde content of the resin. Preferably the adhesive composition comprises a formaldehyde: phenol ratio from about 1.2:1 to about 3:1. This invention is also directed to a resin composition wherein a portion of the phenol within a formaldehyde phenol resin is replaced with NR.
This invention also relates to mixtures of natural resin, comprising whole-oil and fractions of whole-oil. Furthermore, this invention is directed to adhesive compositions and industrial resins comprising natural resin mixtures. This invention also includes phenol-containing formaldehyde resins comprising natural resin, or natural resin mixtures that replaces up to 100% of the phenol content of the phenol-containing resin.
This invention also embraces a wood product prepared using the adhesive compositions as defined above. Preferably, the wood product is selected from the group consisting of laminated wood, plywood, particle board, high density particle board, oriented strand board, medium density fiber board, hardboard or wafer board. Furthermore, the wood product prepared using the adhesive composition of this invention is used for exterior, interior or both interior and exterior applications.
This invention also pertains to industrial phenol formaldehyde resin products including mouldings, linings, insulation, foundry materials, brake linings, grit binders, for example to be used within abrasives such as sand paper, and the like.
Use of a fast pyrolysis process to produce the bio-oil is beneficial in that the fast pyrolysis process depolymerizes and homogenizes the natural glue component of wood, that being lignin, while at the same time other constituents are also depolymerized including cellulose and hemicellulose. The beneficial components are enhanced within NR following the step of distillation/evaporation. The yield of NR, depending upon the biomass feedstock and the fraction of bio-oil used for NR preparation via distillation/evaporation, varies from 15-60% of the feedstock and exhibits properties that are useful within, for example, phenol-containing, or urea-containing formaldehyde resin compositions. The natural resin so produced can be substituted for some of the phenol and formaldehyde, content within phenol-containing formaldehyde resins, and such formulations meet or exceed current phenol formaldehyde resin industry specifications. Furthermore, NR can substitute for some of the formaldehyde within urea-containing formaldehyde resins. With removal of the organic acids, the NR can completely substitute for the phenol content in phenol resins, and can also be used within urea-containing formaldehyde resin formulations.
This summary of the invention does not necessarily describe all necessary features of the invention but that the invention may also reside in a sub-combination of the described features.